Circuit arrangement for character display on a television display screen

ABSTRACT

A circulating storage device for TV character generating apparatus using a separate circulating storage element for each line of the TV scan.

lJnitefl States Patent 1 1111 3,735,4

Nussbaum et al. 1 May 22, 1973 CIRCUIT ARRANGEMENT FOR [56] References Cited CHARACTER DISPLAY ON A TELEVISION DISPLAY SCREEN UNITED STATES PATENTS [75] Inventors; G Nussbaum; Reimer Von 3,559,208 1/1971 Giugno et a]. ..340/324 AD 05w, both f Bremen Germany 3,598,911 8/l97l Helbig ..340/324 AD 3,609,743 9/1971 LaSOff et al. ..34o 324 AD [73] Asslgneez U.S. Philips Corporation, New 3,388,391 6/1968 Clark ..340/324 A York, N.Y. 3,400,377 9/1968 Lee ..340/324 A [22] Filed: 13 1970 3,531,796 9/1970 Kiesling ..340/324 A 3,345,458 10/1967 c616 et al... ....340 324 A x pp 63,410 3,528,068 9/1970 Johnson ..340 324 A [30] Foreign Application Priority Data Primary Examiner-David L- Trafton Sept. 19, 1969 Germany ..P 19 47 532.2 Atwmey Frank Tnfa" 521 us. (:1. ...340/324 AD, 178/DIG. 22, 340/1725 [57] ABSTRACT [51 Int. Cl ..G06f 3/14 1 A circulating swrage device for TV character generab [58] Field of Search ..340/324 A ing apparatus using a separate circulating storage element for each line of the TV scan.

8 Claims, 7 Drawing Figures ,VLi VLZ VH1 DELAY LlNES L W L'INES LINEQSTORE VLZ PATENTEB W22 l 3 7 3 5 3 84 SHEET 1 OF 3 INPUT FLIP FLOP AMPLIFIERS E Tr Lv PH a anratop K VL D 9 x A StB MODULATOR STORE CONTROL CONDUCTOR TU n E vu \lL2 \lLn DELAY LINES DELAY LINES LINE STORE INVEN'I'OR) H. G. NUSSBAUM R. von OSTEN AGENT PATENTEL W22 3.735 384 SHEET 2 [IF 3 CONTROL DEVICE St SA 'SYNCHRONIZING STAGE I .[E/A BSp ZSp V 26 V MS MIXING INPUT OUTPUT FRAME LINE STORE STAGE STAGE sToRE cI-IARAcTER GENERATOR MONITOR T MR IL KEYBOARD HORIZONTAL A2 VERTICAL HSA SYNCHRONIZING /VSA STAGE CHARACTER I I v R R BIT COUNTER V CI. IN E TE COUNTER -I INE couNTER -CENTRAL CLOCK DECODER TK PULSE GENERATOR 2G COMPARISON CHARCTER CIRCUITS TOR COMPARISON GENE v1 rcIRcuIT v2 V3 KEYBOAYRD T v) 20 OECODER StB 22% C co TROL N I grg ggTAL CH CV SS DEVICE c uN vERTIcAL cuRsoR o TER COUNTER StZ I INPUT OUTPUT FRAME STAQE sTo E INVENTOR;

H. G. NUSSBAUM R. von OSTEN AGFM PAIENTED IIAY 2 2 I973 SHEET 3 OF 3 SWITCH VLI ,swncuss I S2 SWITCH] VLn SWITCH Fig.5

VLZ

SHIFT REGISTER DELAY LINE FIg.6

StZ 2 1 INVENTORS H. G. NUSSBAUM AGENT CIRCUIT ARRANGEMENT FOR CHARACTER DISPLAY ON A TELEVISION DISPLAY SCREEN The invention relates to a circuit arrangement for the display of digital information in the form of characters on a television display screen, said arrangement comprising a circulation store in which the information is circulated once during the display process of one line of the television frame, a decoder and a character generator for the character to be displayed, there being provided a controlling device that causes at a given instant only that information to appear at the outputs of the circulation store which serves for the character to be generated at said instant in the character generator and to be displayed on the display screen, the circulation store having a capacity which is sufficient for storing the whole digital information of the character to be displayed on one line, while a buffer store with a selection device is provided in which the whole information for the characters to be displayed simultaneously on the display screen can be stored and while the control device comprises a character counter that counts the number of characters on each line and a line counter, which counters control the selection device so that the digital information for one line of characters can be transferred from the buffer store to the circulation store during a time which corresponds at the most with the display time of the interspace between the lines on the display screen. Such an arrangement is known from Dutch Pat. application No. 6802281. The buffer store may be a disc or drum store, or as stated in said patent application, a core store, which may be formed by part of a computer store, whereas the circulation store may be formed by a television delay line.

If, however, the display device is connected to the computer through long conductors, it is not economical to use magneto-mechanical storage elements for the buffer store, while it is no longer possible to use part of the computer store. The use of a core store is less advantageous since the required capacity required of 1,000 to 2,000 words of 6 to 8 bits is too low.

The invention provides an advantageous embodiment of the buffer store and is characterized in that the buffer store comprises a plurality n of identical circulation stores for one line each said number n corresponding to the maximum number of lines of characters to' be displayed in sequence by a circulation store, and in that, all circulation stores are driven in synchronizm because the signals from the control device are also utilized for controlling all circulation stores.

Since the control device has at any rate to be provided for controlling the circulation store for each line to be displayed, the control is practically not complicated further by the use of identical circulation stores for the buffer store. This advantage becomes particularly manifest, if passive circulation stores are employed, for example, the aforesaid television delay lines or electronic shift registers. In order to provide a higher capacity of the buffer store, the separate store modules used as circulation stores may be arranged in series or in parallel or in a combined system, there being thus provided individual advantages as will be explained hereinafter. In this way the whole image contents are stored in a higher-capacity store and only the characters required for one line are consecutively taken over line by line in a store module of the kind described,

which is scanned in synchronism with the deflection of the electron beam in the display tube several times in sequence. The store which contains the whole image contents can be driven with the same frequency as the store module for scanning the line, but it may alternatively operate at a slower rate, i.e., when the information is scanned in a time prolonged to the extent corresponding to the number of frame lines to be written for one line of characters. A line of characters is taken over from the slower-action image store into the quickaction store module during the writing of the interspace between two lines, because during this interval no information is written on the display screen. Because the characters are stored in the modules in coded form, the output signals drive a character generator which provides at its output the signals required for controlling the intensity of the electron beam and the configuration of the display pattern.

The store modules set forth may be advantageously embodied by ultrasonic delay lines because owing to the comparatively low sound rate they have long delay times and high storing capacity with small dimensions. Dynamic stores delay lines may be used, which are built up as wires with magnetostriction converters or glass or quartz conductors with quartzor piezo-electric converters. Particularly economical are in this case television delay lines having a delay time of 64/p.sec in accordance with the PAL system for use in color television reception, since they are manufactured in large series. Instead of these glass delay lines, also one may employ dynamically operating, highly integrated MOS shift registers that operate as delay lines. Also, statically operating, highly integrated, shift registers may be employed for this purpose. The advantages of the latter registers for the store modules reside in the simple organization of the store control because the circulation time of the information may be chosen substantially arbitrarily so that the scanning frequency may be adapted to the writing speed of the electron beam on the display screen, as a result of which the characters to be displayed are supplied by the register at the correct instant and appear at the corresponding place on the display screen. In this case a complicated address selector (for example, a diode matrix) may be dispensed with, whereas this has hitherto been required in stores hitherto used in display screen apparatus.

Moreover, each store module requires only one driver and one read amplifier. Therefore, the use of such delay lines allows one to design a store structure whose cost per bit is considerably lower than that of other known storing processes.

A further advantageous embodiment is characterized in that a store for one character is connected after the circulation store for the line to be displayed and in that the information can be fed back to the input of the circulation store optionally either from the output of the circulation store or from the output of the store connected after the circulation store. Thus the information can be shifted over one character space.

In order to permit of shifting the information over one place optionally forwards or backwards, a further embodiment of the invention is characterized in that the capacity of the circulation store for each line to be displayed is one character lower than the number of characters that may be displayed on one line, in that after the circulation store two stores for one character each are connected in series and in that the information can be fed back to the input of the circulation store optionally from the output of the circulation store or from the output of the first or of the second series-connected stores.

In order to permit of indicating a given place of the display screen a further embodiment of the invention is characterized in that for the horizontal and vertical positions of a character to be supplied from without and/or for a character region to be indicated on the display screen, adjustable stores are provided, the outputs of which lead to comparison circuits which compare the contents of said stores with the positions of the character counter counting the number of characters on one line and of the line counter and in that equality results in a signal which changes the representation of the character region with the adjusted position and controls the introduction of supplied characterinto the frame store, if necessary, with the aid of a further control-device.

A further embodiment of the invention is characterized in that the signal changing the character region with the adjusted position inverts the display signal.

Embodiments of the invention will be described more fully with reference to the drawings. Therein FIG. 1 shows a store module comprising a glass delay line;

FIG. 2 a block diagram of the frame and line store (series connection);

FIG. 3 a block diagram of a display device;

FIG. 4 a block diagram of the control-part and the store of a display device;

FIG. 5 a block diagram of a frame store in parallel connection;

FIG. 6 a block diagram of a line store with a righthand shift;

FIG. 7 a block diagram of a line store with a left-hand or right-hand shift;

FIG. 1 shows the block diagram of a store module comprising a glass delay line. The pulses to be stored are supplied via the conductor E and they are read via the conductor A. By means of the control-conductor StB it is determined whether new pulses have to be taken over from E or whether they have to be re-stored from A. Via the conductor Tt clock pulses are applied whose frequency matches the transmission properties of the conductor and the desired storing capacity or whose frequency is derived from one or from all delay lines or is synchronized therewith.

The clock pulse converter TU provides the clock pulses for the input and output flip-flops employed FFl and FF2 and for the modulator 4. In this embodiment the modulator is formed by an And-gate by means of which the store VL can be erased, for example, by amplitude modulation. Tr and LV designate amplifiers. When the storing capacity of a module is not sufficient for one line of characters, two or more of them may be used in parallel or in series.

FIG. 2 shows the block diagram of a complete store of a display apparatus comprising a frame store formed by series-connected delay lines VLl to VLn and a line store VLZ. The data arrives from a computer via the conductor E under the control of selection means (address register) via the conductor StB. The output of the store data takes place via conductor A. The information to be displayed is taken over line by line via the conductor Z into the line store VLZ under the control, of StZ. The number of cycles per written line in the line store is equal to or higher than the number of frame lines required for the display of a written line. The characters stored in coded form are derived from ZA and fed to a character generator which converts them into a dot raster.

The block diagram of FIG. 3 shows a possible construction of a display apparatus. The data to be displayed are fed in to the apparatus either by the keyboard T or by a computer via the input/output stage EIA and stored in the frame store BSp. In accordance with the frequency of a control-device St the data are called up cyclically from the frame store and applied via the line store 25p to the character generator ZG, which converts the coded characters into a frame signal that controls the intensity of an electron beam in the display part and hence the formation of the image. The control-part St produces the synchronizing and scanning signals for controlling the electron beam across the display screen in the synchronizing stage SA, mixes them with the frame signal in the mixing stage MS and applies them to the monitor MR.

It is often desirable for specified input data to appear on the display screen at an adjustable place. For this purpose these data have to be written at the corresponding place in the frame store, which means that there must be an address selector for the frame store. This address selector may be used with particular advantage in the frame store constructed according to the invention for additional indication of the place on the display screen where the applied character has to appear, by means of a so-called cursor by having this character or the associated character field distinguished from its environments by a frame signal affected accordingly. If, for example, the frame signal is inverted at this place, the applied character appears in the adjusted character field in dark color on a bright background, whereas the other character appear bright on a dark background.

By way of example of an embodiment of such a cursor in connection with address selection FIG. 4 shows a block diagram of the control-part and of the store of a display device. In this case the frequency dividers required for the synchronization of the electron beam are connected through comparison circuits to the counters for disposing the cursor so that they form at the same time the selection stages for the frame and line stores. The arrangement operates as follows:

A central clock-pulse generator Tk, which is also used for controlling the store modules, drives a counter circuit which comprises a bit counter BZ counting the number of bits per character, a character counter 22 counting the number of characters per line, a line counter LZ counting the number of television lines in each written line (including the space between the lines) and a line counter counting the number of written lines per television frame. These counters are decoded, and in the stage BSA and in the stage VSA the horizontal and vertical synchronizing and read pulses respectively are produced. Characters may be supplied to the frame store BSp by the computer or via the keyboard T via the input and output stage E/A. The storing place is marked on the display screen by the cursor and may be selected by means of the keyboard T or by the computer via the input and output stage BIA with the aid of two counters (the horizontal cursor counter CH and the vertical cursor counter CV). These counters are compared via the comparison circuits V1 to V3 with the counters ZZ, LZ and ZIZ. The cursor is displayed on the screen when the positions of the cursor counters CH and CV are equal to those of ZZ and ZIZ. The position equality is indicated by the comparison circuits V1 and V3; the AND-gate C combines their output signals and provides a signal every time when the electron beam on the display screen passes over the place which corresponds to the positions of the counters CH and 'CV. The comparison circuits V1 and V2 compare CH with ZZ and CV with LZ and their output signals are combined by the AND-gate StB, which controls the supply of data by the keyboard or the computer to the frame store BSp. This is possible because the character counter ZZ circulates in synchronism with the store modules, when in addition the number of written lines per frame the number of seriesconnected modules as shown in FIG. 2) is equal to the number of television lines of written line or, equal to the latter number multiplied by 2" (k natural number).

The line-wise transfer of the stored data from the frame store 88;; to the line store for display purposes is controlled by the store control device SSt. This is performed in accordance with the positions of the counters LZ and ZIZ, which are decoded by the decoders LD and ZD. The information circulating in the line store is applied to the character generator ZG. Moreover, from the decoder ID the character generator receives the information which frame line of the character line has to be displayed and it supplies a frame signal that corresponds to the dot raster of the character to be displayed, which frame signal is mixed in the mixing stage MS with the synchronizing and read signals to form the output signal MR. Thus a complete frame scanning synchronizing signal (BAS) is obtained, which is applied to a monitor.

The cursor can be displayed in a simple and very distinct manner because the inverter CI inverts the frame signal during the time when the beam passes over the place to be marked.

FIG. 5 shows a further embodiment in which the information circulates in parallel through the delay lines VLl to VLn. The switches S1 to Sn control the data supply, the switch SA controls the delivery of data and the switch SZ controls the display on the screen Z. This construction has the advantage that the time required for scanning amounts to 64p.sec at the most, whereas in the construction of FIG. 2 it may be n-times 64p.sec. Moreover, in this'case the separate line store may even be dispensed with, when each circulation store invariably covers one line. In this case, however, a greater number of switches is required. This construction will be chosen when high transmission rates to and from the computer are desired or when the display device has to display only a few lines.

The arrangement shown in FIG. 2 will be preferred for devices having more lines or lower transmission rates. It is furthermore possible to use a combination of the two possible constructions, for example, by connecting m/2 lines in series and by driving the two groups in parallel (here, m is an even number).

FIG. 6 shows an arrangement of the line store of FIG. 2, in which the output signal of the delay line VLZ is applied to a shift register SR, from which it is applied to a character display device ZA. By means of a signal on the control-conductor StZ the information arriving at the input Z is taken over by the frame store. In accordance with the signals across the control conductors S1 and S2 information can then be re-stored by V or SR. If during the display of a line the feedback storing is switched over from V to SR, it is ensured that the characters arriving after this changeover are shifted by one place to the right on the screen. At the end of the line there the feedback storing is switched back to V.

FIG. 7 shows a corresponding circuit arrangement, in which a shift may be performed both to the right and to the left. For this purpose the delay line VLZ of FIG. 6 is replaced by a delay line VL, the capacity of which is one character lower than that of VLZ, which character is stored in the shift register SRI. In accordance with the control signals at S1 to S3 the feedback storing is obtained from V (normal), from SRII (for a right-hand shift) or from VL (for a left-hand shift). The shortened line VL is obtained by grinding off the delay line VLZ, originally in accordance with the PAL standard by the corresponding difference in length.

Instead thereof the cycle time and hence the sweeping time of the beam may be prolonged by one character. In this case the transittime of the frame store has to be prolonged by a number of characters corresponding to the number of lines on the display screen, which may be achieved by composing the frame store from delay lines with which one shift register for one character is individually connected in series or by inserting an additional delay line having a corresponding overall delay time. The invention is not restricted to these embodiments or to the use of glass delay lines; other circulation stores, for example, electronic shift registers may also be employed.

What is claimed is:

1. A circuit arrangement for the display of digital information in the form of characters on a television display screen, comprising a buffer store for receiving in coded character information and for storing sufficient information to simultaneously display characters on the entire screen of a television display, the buffer store further comprising a plurality of N identical circulating stores each capable of storing the information of one line of the television display where N is the maximum number of lines of the television display, a further circulating store connected to the buffer store for storing one line of television display information, a control device connected to the circulating store and to the buffer store for providing signals circulating the information in the buffer store once each scan of the television display and providing signals for reading selected information from the buffer into the further circulating store and for providing signals to the further circulating store for interrogating preselected portions of the information in the further circulating store, a character generator connected to the further circulating store for converting the information from the further circulating store into signals compatible with the television display, the control device comprising a character counter for counting the number of character on a line of television display and a line counter, a selection device in the buffer store responsive to signals from the counters for transferring character information from the buffer store to the further circulating store at a time corresponding to the interval between lines on the television display.

2. A circuit arrangement as claimed in claim 1, characterized in that the buffer store comprises seriesconnected circulation stores.

3. A circuit arrangement as claimed in claim 1, characterized in that the buffer store comprises parallelconnected circulation stores.

4. A circuit arrangement as claimed in claim 1, characterized in that the buffer store comprises circulation stores connected group-side in parallel and in series.

5. A circuit arrangement as claimed in claim 1, characterized in that a store (SR) for one character is connected after the further circulation store for the line to be displayed (VLZ) and in that the information can be fed back to the input of the further circulation store optionally either from the output (V) of the further circulation store or from the output of the store connected after the circulation store.

6. A circuit arrangement as claimed in claim 1, characterized in that the capacity of the circulation store for each line to be displayed (VL) is one character lower than the number of characters that may be displayed on one line, in that after the circulation store (VL) two stores (SRl, SRll) for one character each are connected in series and in that the information can be fed back to the input of the circulation store optionally from the output of the circulation store (VL) or from the output of the first (SR1, V) or of the second (SRIl) series-connected stores.

7. A circuit arrangement as claimed in claim 1 characterized in that for the horizontal and vertical positions of a character to be supplied from without and/or for a character region to be indicated on the display screen adjustable stores (CH, CV, respectively) are provided, the outputs of which lead to comparison circuits (V1, V2, V3), which compare the contents of these stores (CH, CV) with the positions of the character counter counting the number of characters on one line (22) and of the line counter (ZIZ) and in that equality results in a signal which changes the representation of the character region with the adjusted position and controls the introduction of a supplied character into the frame store (BSp), if necessary, with the aid of a further control-device.

8. A circuit arrangement as claimed in claim 7, characterized in that the signal changing the character region with the adjusted position inverts the display signal. 

1. A circuit arrangement for the display of digital information in the form of characters on a television display screen, comprising a buffer store for receiving in coded character information and for storing sufficient information to simultaneously display characters on the entire screen of a television display, the buffer store further comprising a plurality of N identical circulating stores each capable of storing the information of one line of the television display where N is the maximum number of lines of the television display, a further circulating store connected to the buffer store for storing one line of television display information, a control device connected to the circulating store and to the buffer store for providing signals circulating the information in the buffer store once each scan of the television display and providing signals for reading selected information from the buffer into the further circulating store and for providing signals to the further circulating store for interrogating preselected portions of the information in the further circulating store, a character generator connected to the further circulating store for converting the information from the further circulating store into signals compatible with the television display, the control device comprising a character counter for counting the number of character on a line of television display and a line counter, a selection device in the buffer store responsive to signals from the counters for transferring character information from the buffer store to the further circulating store at a time corresponding to the interval between lines on the television display.
 2. A circuit arrangement as claimed in claim 1, characterized in that the buffer store comprises series-connected circulation stores.
 3. A circuit arrangement as claimed in claim 1, characterized in that the buffer store comprises parallel-connected circulation stores.
 4. A circuit arrangement as claimed in claim 1, characterized in that the buffer store comprises circulation stores connected group-side in parallel and in series.
 5. A circuit arrangement as claimed in claim 1, characterized in that a store (SR) for one character is connected after the further circulation store for the line to be displayed (VLZ) and in that the information can be fed back to the input of the further circulation store optionally either from the output (V) of the further circulation store or from the output of the store connected after the circulation store.
 6. A circuit arrangement as claimed in claim 1, characterized in that the capacity of the circulation store for each line to be displayed (VL) is one character lower than the number of characters that may be displayed on one line, in that after the circulation store (VL) two stores (SRI, SRII) for one character each are connected in series and in that the information can be fed back to the input of the circulation store optionally from the output of the circulation store (VL) or from the output of the first (SRI, V) or of the second (SRII) series-connected stores.
 7. A circuit arrangement as claimed in claim 1 characterized in that for the horizontal and vertical positions of a character to be supplied from without and/or for a character region to be indicated on the display screen adjustable stores (CH, CV, respectively) are provided, the outputs of which lead to comparison circuits (V1, V2, V3), which compare the contents of these stores (CH, CV) with the positions of the character counter counting the number of characters on one line (ZZ) and of the line counter (ZIZ) and in that equality results in a signal which changes thE representation of the character region with the adjusted position and controls the introduction of a supplied character into the frame store (BSp), if necessary, with the aid of a further control-device.
 8. A circuit arrangement as claimed in claim 7, characterized in that the signal changing the character region with the adjusted position inverts the display signal. 